Safety burner control apparatus



Oct. 11, 1955 c. J. BISHOFBERGER 2,720,255

SAFETY BURNER CONTROL APPARATUS Fild Jan. 9, 1955 ;64 9 203 44- {202 I mM I 56 H 73 691,. ,n l v? I 7 ION HEATING=42-CLOSES,43OPENS,44 OPENS 52-53 |Q-WHEEQEQEQ1E i P 1 I i l as . 3 I22 I04 INVENTOR. I WAN 557 CARLBISHOFBERGER Y ION HEATING= 42 CLOSES, 43 OPENS, 44 OPENS a i, g e

| ON COOLIN 42 OPENS, 44 CLOSES, 43 CLOS'ES h ATTORNEY United StatesPatent SAFETY BURNER CONTROL APPARATUS Carl J. Bishofberger,Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company,Minneapolis, Minn., a corporation of Delaware Application January 9,1953, Serial No. 330,523

7 Claims. (Cl. 15828) This invention relates to a burner controlapparatus making use of a burner control relay, a safety cutout device,and a combustion responsive means, the control apparatus providing aninitial energizing circuit and a nonpickup holding circuit for therelay, with the non-pickup holding circuit being controlled both by thecombustion responsive means and by in contacts of the relay.

Specifically, this invention is an improvement over the burner controlapparatus disclosed in the co-pending application of Carl D. Ward,Serial No. 280,103, filed April 2, 1952.

The burner control apparatus disclosed in the above mentioned co-pendingapplication incorporates a burner control relay in a circuit including asafety cutout device, an ignition timer, and flame responsive means,with the above mentioned components connected to provide an initialenergizing circuit and a holding circuit for the relay, these circuitsbeing controlled only by the flame responsive means. In this controlapparatus the momentary opening and re-closing of the room thermostatduring a particular time in the operating cycle of this controldeenergizes the burner, however, the relay remains partially energizedthrough the non-pickup holding circuit which includes the actuator forthe ignition timer.

It has been found that in this condition of operation, while the burnercontrol apparatus operates in a safe manner, there is a tendency for therelay to buzz or chatter due to the energization through the non-pickupholding circuit. This noise tends to travel up the heating ducts of thefurnace and creates an unpleasant sensation in the area being heated.Also, the actuator of the ignition timer is not completely deenergizedand, when a bi-metal type timer is used, the recycling of the control iswith a shortened ignition period.

It is therefore an object of the present invention to provide animproved burner control apparatus having ignition timing means whereinimmediate recycling of the burner will not result in a shortenedignition period.

It is a further object of the present invention to provide an improvedburner control apparatus having a relay with an initial energizingcircuit including a safety switch actuator and having a non-pickupholding circuit including current limiting impedance means, with thenon-pickup holding circuit being completed by in contacts of the relayand with flame responsive means arranged to provide for recycle on flamefailure.

It is a further object of the invention to provide an improved burnercontrol apparatus having a burner control relay with an initialenergizing circuit including closed cold contacts of a flame responsivemeans and a safety cut-out means, and having a non pick-up holdingcircuit including a closed cold switch and closed hot switch of theflame responsive means, ignition timing means, and in contacts of therelay, the closed hot and closed cold switches being arranged to giverecycle upon flame failure and the in contacts of the relay preventingpartial energization of the ignition timer or relay during recycle.

It is a further object of the present invention to provide an improvedburner control apparatus having burner control means, safety cutoutmeans, ignition timing means, and flame responsive means with the abovenamed means connected to allow recycle on flame failure, to prevent evenlimited energization of the ignition timing means or burner controlmeans during recycle, and to provide an interlock between the energizingcircuit for the apparatus and the ignition timing means.

These and other objects will readily become apparent as the followingspecification is read in the light of the accompanying drawing in whichFigure 1 is a showing of the improved burner control apparatus, and

Figure 2 is a showing of a modification of the improved burner controlapparatus.

Referring specifically to Figure 1, a fuel burner unit 10 is shownhaving a fuel burner 11 and an ignition means 12. The burner unit 10 iscontrolled by the improved burner control apparatus shown within brokenlines 13, and the apparatus 13 is under the control of the thermostatshown within broken lines 14, which thermostat, upon the need foroperation of the burner unit 10, closes contacts 15 and 16.

Referring specifically to the improved burner control apparatus 13, aburner control relay 17 is provided having a relay winding or actuator18 and an armature 19. The armature 19 of relay 17 is shown in itsinoperative or deenergized position and is provided with bridging bars20, 21, and 22. Upon energization of relay Winding 18, the armaturemoves bridging bar 20 into engagement with in contact 23, bridging bar21 into engagement with the in contacts 24 and 25, and bridging bar 22into engagement with in contacts 26 and 27. A switch which is closedwhen relay 17 is deenergized is provided for the relay 17 and includesstationary contact 28 and contact blade 29 connected to and movable withthe in contact 27 Upon energization of the relay winding 18, armature 19moves bridging bars 20, 21, and 22 into engagement with the in contactsand due to the press back of the relay the in contacts 23 through 27 aremoved to the left to broken line position 30. The movement of the incontacts to this broken line position 30 moves the contact blade 29 tothe left and causes the contact blade 29 to disengage the stationary outcontact 28.

Also included within the burner control apparatus 13 is a safety cutoutdevice 31 having normally closed contacts 32 and 33, a bi-metal member34, a reset acactuator 35, and an electrically energizable actuatingheater 36. Upon a predetermined time period of energization of theheater 36, the bi-metal 34 warps to the right out from under thenormally closed contacts 32 and 33 to allow the contacts to disengage.Upon subsequent cooling of the bi-metal member 34, the reset actuator 35can be depressed to reset the contacts 32 and 33 to their normalposition as shown in Figure l.

A timer 37 is provided having a closed cold switch including contact 38,a bi-metal member 39, and an electrically energizable actuating heater40. After a predetermined time period of energization of heater 40 abovea given minimum energization level, the bi-metal element 39 warps to theleft to disengage the contact 33. Upon the bi-metal element 39 cooling,the element 39 again engages contact 38 as shown in Figure l.

A combustion responsive means 41 is shown having a closed hot switch 42,a first closed cold switch 43, and a second closed cold switch 44. Abimetal actuator is shown at 45 and is normally located to be responsiveto the presence or absence of combustion at the burner unit 10. Thebimetal actuator 45 is effective upon heating to move to the left asshown by the arrow in Figure 1. Movement of bimetal actuator 4-5 istransmitted by 3 means of a rod, shown by dotted line 46, and by members288 and 201 to the switches 42, 43 and 44.

The members 200 and 201 are mounted in slip friction engagement with therod, shown by dotted line 46, and moved with the rod until sufiicientforce is applied to stop such movement, at which time the members 280and 201 will remain stationary and slide upon the rod.

The blades upon which the switches 43 and 44 are mounted are biased sothat as member 200 moves to the left the switches 43 and 44 also move tothe left until stops 202 and 283 are engaged to cause switches 43 and 44respectively to open. The blade upon which righthand member of switch 42is mounted is biased to the right to engage member 201.

The combustion responsive means 41 is shown in the cold position inFigure 1, that is, with no flame present at the burner unit 10. Uponcombustion being established at the burner unit 10, the bimetal actuator45 begins to move to the left. This movement causes members 200 and 201to also move to the left. When member 2111 has moved a predetermineddistance, closed hot switch 42 closes. Subsequently, when member 200 hasmoved a predetermined distance, the right-hand member of closed coldswitch 43 engages stop 202 to stop this member. Further movement ofmember 200 causes closed cold switch 43 to open.

Again after a short time of movement, stop 203 engages the common memberof closed cold switches 43 and 44 and further movement of member 200 tothe left causes closed cold switch 44 to open.

When combustion ceases at the burner unit 10, the bimetal actuator 45cools and moves to the right to the position shown in Figure 1. Firstinitial movement to the right causes member 261 to also move to theright and open thereby closed hot switch 42. Further movement to theright causes member 200 to close closed cold switch 44. Still furthermovement to the right causes closed cold switch 43 to be closed.

A transformer 47 having a primary 48 and a secondary 49 is shownassociated within the burner control apparatus 13 to supply power tocircuits which include the burner control relay 17, the timer 37, thesafety cutout device 31, and the closed hot and closed cold switches ofthe combustion responsive means 41. A plurality of ter minals are alsoassociated with the burner control apparatus 13. The terminals 50 and 51are the power input terminals to the burner control apparatus 13 and areadapted to be connected to a source of electrical power, which power issupplied to the burner unit under the control of the burner controlapparatus 13 and the thermostat 14. The terminals 52 and 53 are adaptedto be connected to the fuel burner 11 and ignition means 12 respectivelyto supply power to the burner unit under the control of the burnercontrol apparatus 13.

In Figure 1 the apparatus is shown in its stand-by condition. That is,the timer 37 has its closed cold switch in closed position, the safetycutout device 31 has its contacts 32 and 33 in engaging position, therelay 1"] is in its deenergized position, and the combustion responsivemeans 41 is in a condition indicating the absence of combustion at theburner unit 10.

Assuming that power is applied to the power input terminals 50 and 51,an initial energizing circuit can be traced for the primary 48 of thetransformer 47 from the power input terminal 50 though the primary 48,conductor 54, bi-metal element 39 and closed contact 38 of timer 37,conductor 55, contact blade 29 and stationary out contact 28 of relay17, conductor 56, and conductor 57 to the power input terminal 51. Fromthis last traced circuit it can be seen that in the stand-by conditionin order for power to be applied to the primary 48 it is necessary firstfor the timer 37 to be in its cold position, and second for the relayarmature 19 to be in its deenergized position such that contact blade 29engages out contact 28.

Assume now that there is a need for operation of the burner unit 10which the thermostat 14. senses by closing contacts 15 and 16. Aninitial energizing circuit can now be traced for the relay 17 from theupper terminal of the secondary 49 through conductor 58, contacts 33 and32 of safety cutout device 31, relay winding 18, conductor 59, contacts15 and 16 of thermostat 14, conductor 6t), conductor 61, actuator 36 ofthe safety cutout device 31, conductor 62, first closed cold switch 43of combustion responsive means 41, and conductor 64 to the lowerterminal of secondary 49.

At this time, the actuator 36 of the safety cutout device 31 isoperatively energized, that is, if the combustion responsive means 41does not operate to indicate the establishment of combustion at theburner unit 10, the safety cutout device 31 will be actuated to theposition where the contacts 32 and 33 are disengaged.

Energization of relay 17 causes the relay armature 19 to move bridgingbars 20, 21, and 22 into engagement with the in contacts 23 through 27.Consider at this time the instant the bridging bars 20, 21 and 22 havejust engaged the in contacts 23 through 27 of the relay 17. The initialenergizing circuit for the primary 48, above traced, is still completedthrough contact blade 29 and out contact 28, however, a holding circuitis now also established for the primary 48. This holding circuit can betraced from the power input terminal 50 through primary 48, conductor54, conductor 65, bridging bar 21 and in contact 24 of relay 17,conductor 66, and conductor 57 to power input terminal 51. The relayarmature 19 completes its movement to take up the press back of therelay and moves the in contacts 23 through 27 to the left to theposition shown by the broken line 30 and therefore it causes contactblade 29 to disengage out contact 28 of the relay 17. This breaks theinitial energizing circuit for the primary 48 for the transformer 47,however, the above traced holding circuit is effective to supply powerto the primary 48 so long as the relay 17 remains in its energizedposition.

The movement of the relay armature 19 to its energized position causespower to be supplied to the burner unit 10 through terminals 52 and 53.The energizing circuit for the burner motor 11 can be traced from powerline 67 through conductor 68, burner motor 11, terminal 52, conductor69, in contact 25 bridging bar 21 and in contact 24 of relay 17,conductor 66, conductor 57, and input terminal 51 to power lineconductor 70. The energizing circuit for the ignition means 12 can betraced from the power line conductor 67 through conductor 68, ignitionmeans 12, terminal 53, conductor 71, in contact 26 bridging bar 22 andcontact 27 of relay 17, conductor 55, contact 38 and bi-metal element 39of timer 37, conductor 65, bridging bar 21 and in contact 24 of relay17, conductor 66, conductor 57, and terminal 51 to power line conductor70.

It will be noted that a circuit, placing actuator 40 in parallel withactuator 36, can be traced from the upper terminal of secondary 49through conductor 58, contacts 33 and 32 of safety cutout device 31,relay 17, conductor 59, contacts 15 and 16 of thermostat 14, conductor60, conductor 76, bridging bar 20 and in contact 23 of relay 17,conductor 75, actuator 40 of timer 37, conductor 74, second closed coldswitch 44 of combustion responsive means 41, and conductor 64 to thelower terminal of secondary 49. It would appear that the actuator 40 isnow operatively energized. However, the relative impedance of actuator40 and actuator 36 is such that so long as the first closed cold switch43 remains closed the actuator 40 is effectively shorted throughactuator 36. By way of illustration, it has been found desirable toselect the following impedance values for the actuators 36 and 40: Ohm

Actuator 36 Actuator 40 The burner control apparatus 13 is now in itsstarting phase wherein the burner motor 11 is energized, the ignitionmeans 12 is energized, the timer 37 is operatively deenergized, and thesafety cutout device 31 is energized.

Assume now that a flame is established at the burner unit 10, thebi-metal actuator 45 of the combustion responsive means 41 will respondto the presence of combustion at the burner unit and will actuate itsassociated closed hot and closed cold switches in the sequence abovedescribed. The bi-metal actuator 45 will first cause the closed hotswitch 42 to close. The closing of the closed hot switch 42 has noeffect at this time since closed hot switch 42 is in parallel withclosed cold switch 44, which switch is already closed.

A short time after the closing of closed hot switch 42, the closed coldswitch 43 opens. This has the effect of deenergizing the actuator 36 ofthe cutout device 31, and at the same time removes the relatively lowimpedance shunt from the actuator 40 of the timer 37. The actuator 40 isnow operatively energized and begins to heat the bi-metal element 39. Inthis condition the relay 17 is maintained energized through the closedhot switch 42 of the combustion responsive means 41, the actuator 40 ofthe timer 37, contact 23 and bridging bar 20 of relay 17, and thermostat14. A short time after the opening of closed cold switch 43, the closedcold switch 44 opens. The function of the closed cold switch 44 is toprovide recycle and will be more completely explained later.

After a predetermined time period of energization of the actuator 40 oftimer 37, the contact 38 disengages bi-metal element 39. This breaks theabove traced initial energizing circuit for the primary 48 oftransformer 47, however it will be remembered that a holdingenergization circuit for the primary 48 has been established upon relay17 being energized. The opening of the closed cold switch of the timer37 also breaks the above traced energizing circuit for the ignitionmeans 12 to thereby turn off the ignition at the burner unit 10.

The burner control apparatus 13 is now in its runing phase with theburner motor 11 energized, the ignition means 12 deenergized, theactuator 36 to safety cutout device 31 deenergized, the bi-metalactuator 45 of the combustion responsive means 41 responding to thepresence of combustion at the burner unit 10, and the actuator 40 of thetimer 37 operatively energized to maintain the timer contact 38disengaged from bi-metal 39.

Assume now that the thermostat 14 has been satisfied by a sufficientperiod of operation of burner unit 10 and has accordingly opened thecontacts 15 and 16. The energizing circuit for relay 17 is thereforebroken and the relay armature 19 returns to its inoperative positionsuch as is shown in Figure 1. This immediately deenergizes the burnerunit 10 and also breaks the holding circuit for the primary 48 oftransformer 47. As shown in Figure 1, the deenergization of relay 17causes contact blade 29 to engage out contact 28 of relay 17.

If as soon as relay 17 is deenergized there is a second call for heat,the relay 17 cannot again be energized since the primary 48 oftransformer 47 is deenergized due to contact 38 disengaging bi-metal 39of timer 37. After a short period of cooling, bi-metal 39 again engagescontact 38. This energizes transformer 47. However, during the timerequired for the bi-metal member 39 to cool, the bi-metal actuator 45 ofthe combustion responsive means 41 has been cooling and first actuatesthe closed hot switch 42 to open position. At this time the closed coldswitches 43 and 44 and the closed hot switch 42 are all open.

A short time after the opening of closed hot switch 42, closed coldswitch 44 closes. At this time the above traced non pick-up holdingcircuit is still open at switch blade 23 and bridging bar of relay 17and therefore relay 17 cannot be energized. If it were not for thenonpickup holding circuit being open at this time, limited energizationof the relay 17 and actuator 40 of timer 37 would occur. This, as abovementioned, would cause an objectionable buzz or chatter of relay 17 andwould also tend to shorten the ignition period. A short time afterclosing of closed cold switch 44, the closed cold switch 43 closes. Ithas been found that the combustion responsive means 41 at this point inthe operation of the apparatus 13 tends to produce an intermittentcondition of engaging and disengaging of closed cold switch 43 for ashort period of time. It will be remembered that the initial energizingcircuit for the relay 17 includes the closed cold switch 43 and if itwere not for the closed cold switch 44 which is closed at this point, itwould be possible for the relay armature 19 to move between itsoperative and inoperative position a number of times before thecombustion responsive means 41 positively closes closed cold switch 43.

To explain more fully the utility of providing the closed cold switch44, consider that the closed cold switch 43 has been closed for a veryshort period of time and then opened due to the inherent characteristicsof bi-metal actuator 45 of the combustion responsive means 41. Theinitial closing of closed cold switch 43 completes the initialenergizing circuit for relay 17 and the relay armature 19 moves to itsoperative position. The closed cold switch 43 now opens, however therelay is maintained energized through the non-pickup holding circuit,above traced, which includes in series with the relay winding 18, theclosed cold switch 44, the actuator 40 of timer 37, and in contact 23and bridging bar 20 of relay 17. It is immediately recognized that withrelay 17 energized the burner unit 10 is energized and bi-metal actuator45 is again subjected to the heat of combustion. In this case the closedcold switch 43, which has been momentarily closed as pointed out above,may not re-close but bimetal actuator 45 will be effective to closeclosed hot switch 42 and then open closed cold switch 44.

However, if combustion is not again established at the burner unit 10,the closed cold switch 43 will again close and be positively closed bybi-metal actuator 45 of cornbustion responsive means 41 to complete theinitial energizing circuit for the relay winding 18 which includes theactuator 36 of safety cutout device 31. Burner unit 10 then remainsenergized until the normally closed contacts 32 and 33 of the safetycutout device 31 are opened in response to a predetermined time periodof energization of the actuator 36. The opening of the contacts 32 and33 deenergizes the relay 17, thereby deenergizing the burner unit 10.The actuator 36 of a safety cutout device 31 is now deenergized and thebi-metal member 34 subsequently cools. The depressing of the actuator 35now resets the contacts 32 and 33 to their engaging position and ifthere is still a call for heat by thermostat 14 the burner controlapparatus 13 begins its cycle to attempt to establish combustion at theburner unit 10.

Species of Figure 2 Referring now specifically to Figure 2, amodification of the apparatus of Figure 1 is shown with the commonelements between the two figures retaining the same reference numerals.In Figure 2 the burner unit 10 has been omitted, however, the conductors68, 69, and 71 connect to the burner unit 10 in the manner shown inFigure 1.

The apparatus of Figure 2 is shown in the stand-by condition, theinitial energizing circuit and holding circuit for the primary 48 oftransformer 47 being identical to that of Figure 1.

Assume now that there is a call for heat by the thermostat 14. Anenergizing circuit can be traced for relay 17 from the upper terminal ofthe secondary 49 through the conductor 100, contacts 15 and 16 ofthermostat 14, conductor 101, normally closed contacts 32 and 33 ofsafety cutout device 31, conductor 102, actuator 36 of safety cutoutdevice 31, conductor 103, closed cold switch 43 of combustion responsivemeans 41, conductor 104, conductor 105, winding 18 of relay 17,conductor 106, and conductor 107 to the lower terminal of secondary 49.Upon energization of relay 17, armature 19 moves to the energizedposition and in the manner above described, the holding circuit ofprimary 48 is established and the initial energizing circuit for theprimary is broken. Also, in the manner above described, the fuel burner11 and ignition means 12 are energized.

Upon the armature 19 moving to the energized position, the bridging bar20 engages in contact 23 of relay 17. The engagement of 20 and 23completes two circuits. The first of these circuits includes theactuator 40 of the timer 37 and can be traced from the upper terminal ofsecondary 49 through conductor 100, contacts 15 and 16 of thermostat 14,conductor 101, contacts 32 and 33 of safety cutout device 31, conductor110, bridging bar 20 and in contact 23 of relay 17, conductor 111,actuator of timer 37, conductor 112 and conductor 107 to the lowerterminal secondary 49. It can be seen that the actuator 40 of the timer37 is now operatively energized and the ignition timing period hasbegun. A predetermined time hereafter the contact 38 will disengage thebi-metal member 39.

The second circuit completed by engagement of bridging bar 20 withincontact 23 is a circuit which includes the blocking resistor 120 and theclosed cold switch 44 of combustion responsive means 41 connected inparallel with the actuator 36 of safety cutout device 31. This shuntcircuit can be seen by tracing the circuit from the lower terminal ofactuator 36 through a conductor 102, conductor 110, bridging bar 20 andin contact 23 of relay 17, conductor 111, conductor 121, blockingresistor 120, conductor 122, closed cold switch 44, closed cold switch43, and conductor 103 to the upper terminal of actuator 36 of safetycutout device 31. At this time the shunt circuit including blockingresistor 120 has very litle effect due to the relative impedances ofblocking resistor 120 and actuator 36. By way of illustration, it hasbeen found desirable to select the following impedance values for theactuator 36 and the blocking resistor 120:

Ohms Blocking resistor 120 50.0 Actuator 36 12.6

From the above values, it can be seen that the above traced shuntcircuit has a high enough impedance so that the current flow through theactuator 36 remains substantially unchanged as the armature 19 of therelay 17 moves to the energized position.

Assume that combustion is now established at the burner unit 10. Thebi-metal actuator of the combustion responsive means 41 will sense thiscombustion and actuate the closed hot and closed cold switches in themanner above described. The closed hot switch 42 is the first switch tobe actuated by the combustion responsive means 41 and will be closed ashort time period after the establishment of combustion at the burnerunit 10. The closing of the closed hot switch 42 has no effect at thistime since it is connected in parallel with the already closed coldswitch 44. A short time thereafter the closed cold switch 43 opens. Thishas two effects. First the actuator 36 of safety cutout device 31 isdeenergized, and secondly a non-pickup holding circuit is establishedfor the relay 17. This non-pickup holding circuit can be traced from theupper terminal of the secondary 49 through the conductor 100, contacts15 and 16- of thermostat 14, conductor 101, contacts 32 and 33 of safetycutout device 31, conductor 110, bridging bar 20 and in contact 23 ofrelay 17, conductor 1'11, conductor 121, blocking resistor 120,conductor 122, closed cold switch 44 in parallel with closed hot switch42 to conductor 105, relay winding 18, conductor 106, and con- '8 ductor107 to the lower terminal of secondary 49. Here again it can be seenthat this non-pickup holding circuit is completed only when relay 17 isenergized.

A short time thereafter the ignition timer 37 is actuated due toenergization of the actuator 40 and causes contact 38 to disengagebimetal 39 to deenergize the ignition means 12 in the manner abovedescribed.

The burner control apparatus 13 is now in the running condition with theburner motor 11 energized, the ignition means 12 deenergized, theactuator 40 of timer 37 energized, the actuator 36 of safety cutoutdevice 31 deenergized, and the relay 17 energized through the nonpickupholding circuit. A short time thereafter the closed cold switch 44opens, however, the opening of this switch at this time has no effectupon the circuit to relay 17 which remains completed through closed hotswitch 42.

Upon satisfaction of the thermostat 14 the contacts 15 and 16 of thethermostat 14 open. This breaks the energizing circuit for the relay 17and the armature 19 moves to the deenergized position to deenergize theburner 10 and to also deenergize the actuator 40 of the timer 37.

Assume now that there is an immediate call for recycle as evidenced bythe contacts 15 and 16 of thermostat 14 again closing. At this time aclosing of the thermostat contacts has no effect since the primary 48 ofthe transformer 47 is deenergized due to the contact 38 being disengagedfrom bi-metal member 39 of timer 37.

A short time thereafter contact 38 engages bi-metal member 39 and thevprimary 48 of transformer 47 is en ergized. During the time required forthe bi-metal member 39 to cool, the bi-metal actuator 45 of thecombustion responsive means 41 has been cooling and first actuates theclosed hot switch 42 to open position. The closed cold switch 44 is nextactuated to closed position however, this has no effect at the presenttime since the non-pickup holding circuit is open at the relay contact23. The fact that the non-pickup holding circuit is open at this timeprevents limited energization of the relay which would tend to cause therelay to hum or chatter.

A short time thereafter the closed cold switch 43 closes to complete theinitial energizing circuit for the relay 17. As above mentioned, it is acharacteristic of the bi-metal actuator 45 of combustion responsivemeans 41 to cause intermittent engagement of the closed cold switch 43when they are first closed due to the actuator 45 cooling. However, oncethe relay armature 19 is moved to the energized position the abovementioned non-pickup holding circuit which includes the closed coldswitch 44, the blocking resistor 120, and the in contact 23 and bridgingbar 20 of relay 17, has been completed and the subsequent momentaryopening of the closed cold switch 43 will not cause the relay 17 to bedeenergized.

The energization of the relay 17 in the manner above described againcauses the burner unit 10 to be cycled to establish flame at the unit.If for some reason flame is not established at the burner unit 10 thesafety cutout device 31 is actuated to open the normally closed contacts32 and 33 in the manner above described with reference to Figure 1.

From the above description of the operation of the present invention asapplied to Figures 1 and 2 it can be seen that the burner controlapparatus 13 provides an initial energizing circuit for the burnercontrol relay 17 and provides a non-pickup holding circuit for the relayto maintain the relay energized after the flame responsive means 41 hasresponded to the presence of combustion at the burner unit 10. It canalso be seen that this nonpickup holding circuit, because it iscontrolled by in contacts of the relay, is ineffective to supply evenlimited energization to the relay 17 when the relay armature 19 is inthe deenergized position and thereby insures that no objectionable noisewill. be generated due to limited energization of the relay 17. It canalso be seen that since the energizing circuit for the actuator 40 oftimer 37 is completed. through in contacts of the relay 17, a

possibility of a shortened ignition period due to premature energizationof the actuator 40 is prevented and actuator 40 can be energized onlywhen the burner control apparatus 13 is going through its cycle ofoperation in the normal manner.

While the present invention has been shown with reference to a first andsecond modification it is understood that the invention is limitedsolely by the scope in the appended claims.

I claim as my invention:

1. A burner control apparatus for use with a fuel burner and meansresponsive to the need for operation of the fuel burner, comprising: asafety switch having an electrically energizable actuator and a normallyclosed switch, said switch opening after a predetermined time period ofenergization of said actuator; a fuel burner control relay having awinding and switching means having at least one switch; flame responsivemeans having first and second switches closed in the absence ofcombustion and a third switch open in the absence of combustion, saidthird switch being connected in parallel with said second switch; asource of power; energizing circuit means for said relay including saidwinding, the normally closed switch and actuator of said safety switch,said first switch of said flame responsive means, and leads adapted tobe connected to means responsive to the need for operation of the fuelburner; current limiting impedance means; and non-pickup holding circuitmeans for said relay including said winding, the switch of said safetyswitch, said one switch of the switching means of said relay, and saidsecond and third switches of said flame responsive means.

2. Burner control apparatus comprising, burner control means having anelectrically energizable actuator and having switching means having afirst switch adapted to be connected to energize a fuel burner when saidactuator is energized; a safety cutout device having an electricallyenergizable actuator and a normally closed switch which opens after apredetermined time period of energization of said actuator; bimetallicflame responsive means having first and second overlapping switcheswhich are closed in the absence of combustion and having a third switchwhich is open in the absence of combustion, said second and thirdswitches being connected in parallel; said flame responsive meansoperating upon the establishment of flame to close said third switch,then open said first switch, and then open said second switch; saidflame responsive means operating upon the subsequent failure ofcombustion to first open said third switch, then close said secondswitch, and then close said first switch; energizing circuit means forsaid burner control means including said burner control means actuator,the normally closed switch and actuator of said safety cutout device,said first switch of said flame responsive means, and means responsiveto the need for operation of the fuel burner; current limiting impedancemeans; and a nonpickup holding circuit for said burner control meansincluding said burner control means actuator, the normally closed switchof said safety cutout device, said second and third switches of saidflame responsive means, said current limiting impedance means, a secondswitch of said switching means of said burner control means which isclosed when said burner control means is energized, and said meansresponsive to the need for operation of the fuel burner.

3. A burner control apparatus comprising: a burner control relay havinga winding and switching means having a first switch adapted to beconnected to energize a fuel burner when said relay is energized; asafety switch having a relatively low impedance actuator and a normallyclosed switch which opens after a predetermined time period ofenergization of said actuator; flame responsive means of the type havinga bi-metal actuator responsive to the heat produced by the establishmentof combustion at the fuel burner, said flame responsive means havingfirst and second pairs of closed cold coritacts and a third pair ofclosed hot contacts, said second and third pair of contacts beingconnected in parallel; said flame responsive means operating upon theestablishment of flame to first close said closed hot contact pair, thenopen said first closed cold contact pair, and then open said secondclosed cold contact pair; said flame responsive means operating upon thefailure of combustion to first open said closed hot contact pair, thenclose said second closed cold contact pair and then open said firstclosed cold contact pair; energizing circuit means for said relayincluding said relay winding, the normally closed switch and therelatively low impedance actuator of said safety switch, said firstclosed cold contact pair, and means responsive to the need for operationof the fuel burner; relatively high impedance current limiting means;non-pickup holding circuit means for said relay including said relaywinding, the normally closed switch of said safety switch, said firstand third pairs of contacts of said flame responsive means, saidrelatively high impedance current limiting means, and a second switch ofsaid switching means of said relay which is closed when said relay isenergized; said non-pickup holding circuit means being substantiallyshort circuited by said energizing circuit means because of the relativeimpedances of said safety switch actuator and said current limitingmeans until said first closed cold contact pair of said flame responsivemeans is opened and being ineffective because of said second switch ofsaid relay switching means to supply even reduced power to said relaywinding upon recycle until said first closed cold contact pair closes asthe bimetal actuator of said flame responsive means cools.

4. A burner control apparatus for use with a fuel burner having ignitionmeans, comprising; a burner control relay having switching means havinga first and a second switch; safety cutout means having a 10W impedanceactuator and a normally closed switch; flame responsive means havingfirst and second closed cold contact pairs and a third closed hotcontact pair, said second and third contact pairs being connected inparallel; energizing circuit means for said relay including saidactuator and normally closed switch of said safety cutout means, saidfirst closed cold contact pair of said flame responsive means, and meansresponsive to the need for operation of the fuel burner; ignition timingmeans having a high impedance actuator and a normally closed switch;nonpickup holding circuit means for said relay including said normallyclosed switch of said safety cutout means, said second and third contactpairs of said flame responsive means, said first switch of saidswitching means of said relay which are closed when said relay isenergized, and said actuator of said ignition timing means; saidnonpickup holding circuit means being substantially shunted by saidenergizing circuit means so long as said first contact pair of saidflame responsive means is closed, said actuator of said ignition timingmeans being effectively energized upon said first contact pair of saidflame responsive means opening to thereby subsequently deenergize theignition means for the fuel burner; a power energizing circuit for saidapparatus including said normally closed switch of said ignition timingmeans, and a power holding circuit for said apparatus including saidsecond switch of said switching means of said relay which is closed whensaid relay is energized.

5. A burner control apparatus for use with a fuel burner having ignitionmeans, comprising; a burner control relay having first and second incontacts; a safety switch having an electrically energizable actuatorand a normally closed switch; flame responsive means having first andsecond pairs of closed cold contacts and a pair of closed hot contacts,said closed hot contacts being connected in parallel with said secondpair of closed cold contacts; energizing circuit means for said relayincluding the actuator and normally closed switch of said safety switch,the first pair of closed cold contacts of said flame responsive means,and means responsive to the need for operation of the fuel burner;current limiting impedance means; non-pickup holding circuit means forsaid relay including said second closed cold contacts of saidcornbustion responsive means, said current limiting impedance means, andsaid first in contacts of said relay; ignition timing means having anactuator and a normally closed switch, an energizing circuit for saidignition timing means actuator including said first in contacts of saidrelay, said actuator opening said normally closed switch of saidignition timing means after a predetermined time period of energizationof said actuator; an initial power energizing circuit for said apparatusincluding said normally closed switch of said ignition timing means; anda power holding circuit for said apparatus including said second incontacts of said relay.

6. A burner control apparatus for use with a fuel burner having ignitionmeans, comprising; a burner control relay having in contacts; a safetyswitch having an electrically energizable actuator and a normally closedswitch; flame responsive means having first and second pairs of closedcold contacts and a pair of closed hot contacts, said closed hotcontacts being connected in parallel with said second pair of closedcold contacts; energizing circuit means for said relay including theactuator and normally closed switch of said safety switch, the firstpair of closed cold contacts of said flame responsive means, and meansresponsive to the need for operation of the fuel burner; currentlimiting impedance means; nonpickup holding circuit means for said relayincluding said second closed cold contacts of said combustion responsivemeans, said current limiting impedance means, and said in contacts ofsaid relay; ignition timing means having an actuator and a normallyclosed switch, and an energizing circuit for said ignition timing meansactuator including said in contacts of said relay, said actuator openingsaid normally closed switch of said ignition timing means after apredetermined time period of energization of said actuator.

7. A burner control apparatus for use with a fuel burner and meansresponsive to the need for operation of the fuel burner, comprising; anelectromagnetic actuator, switching means controlled by said actuatorand having a first switch adapted to be connected to energize a fuelburner when said electromagnetic actuator is energized, an electricallyenergizable safety cutout actuator and cutout switching means controlledthereby, flame responsive means having first and second switches closedin the absence of flame and a third switch open in the absence of flame,said third switch being connected in parallel with said second switch, asource of power, energizing circuit means connecting saidelectromagnetic actuator to said source of power including said safetycutout actuator, said cutout switching means, leads adapted to beconnected to the means responsive to the need for operation of the fuelburner, and said first switch of said flame responsive means; currentlimiting impedance means; and a non-pickup holding circuit for saidelectromagnetic actuator connecting said electromagnetic actuator tosaid source of power including said second and third switches of saidflame responsive means, said impedance means, and a second switch of theswitching means of said electromagnetic actuator.

References Cited in the file of this patent UNITED STATES PATENTS2,075,289 Judson Mar. 30, 1937 2,086,823 Shaw July 13, 1937 2,370,847Dempster Mar. 6, 1945 2,604,148 Witherspoon July 22, 1952

